Notwithstanding the significant progress exhibited by girls in math and science course taking and performance in recent years, concerns regarding the number of females pursuing careers in certain fields in Science, Technology, Engineering, and Mathematics (STEM) remain. Females are well represented in both undergraduate- and master-level programs in the biological and medical sciences; however, they continue to be underrepresented at all levels of training in mathematics, physical, engineering, and computer sciences. Based on Expectancy-Value theory, the opportunities provided by teachers and parents and the experiences associated with STEM-related activities in school and family shape the development of an individual's self- efficacy, interests, task values, and long-term life goals which in turn, influence educational and career choices (e.g., college majors and occupations) in STEM and non-STEM fields. Gender differences in the decision to enter STEM fields may be associated with gendered differences in these motivational beliefs. Unfortunately, extant research tends to be cross-sectional, ignoring changes that occur across major school transitions and thus failing to document normative changes in self-efficacy, interests, values, attitudes toward, and performance in math and science. In addition, much of the research takes a deficit perspective focusing on the shortcomings of individuals or females as opposed to identifying the psychological and contextual factors that predict individual success and pursuit of STEM-related careers. Using the Longitudinal Study of American Youth (LSAY), a longitudinal study of a national sample of 3116 public school students in the United States, the PI seeks to investigate the development of STEM-related self-efficacy, interests, and valuing during secondary school and then to relate these motivational beliefs to STEM-related educational and career choices. Specifically, this project will (Aim 1) investigate developmental changes and gender differences in adolescent motivational beliefs (e.g., self-efficacy, interests, task value) s adolescents proceed from middle school through high school, (Aim 2) examine whether family-based experiences influence adolescent motivational beliefs, which in turn, predict their academic performance and educational and career choices in STEM and non-STEM areas, (Aim 3) determine whether family and motivational factors and processes leading to different patterns and pathways in the pursuit of STEM and non-STEM careers differ by gender.